Admixture for optimizing addition of EO/PO plasticizers

Abstract

In the preparation of aqueous cement compositions containing a plasticizer, such as an EO/PO polymer-containing plasticizer, or EO/PO comb polymer-containing plasticizer, and further containing clay, such as a smectite clay, which expands when in contact with water, the step of providing an agent operative to modify the clay whereby the plasticizer absorbing capability of the clay is reduced. In exemplary methods of the invention, the plasticizer is an EO/PO (e.g., oxyalkylene) plasticizer and preferably an EO/PO comb polymer, and the clay-activity-modifying agent may comprise an inorganic cation, an organic cation, a polar organic molecule capable of being absorbed by the clay, a clay dispersant (such as a polyphosphate), or a mixture thereof. For clay-activity-modifying agents which comprise a cation or a polar organic molecule, the agent is preferably added to the clay before water is introduced to the clay. For clay dispersant agents and some organic cations such as quaternary amines (which have a strong affinity for cationic exchange with the clay), the agent may be added before, during, or after water is introduced to the clay.

What is claimed is:  
     
       1. An admixture composition comprising: 
       (A) a comb polymer operative to plasticize a hydratable cementitious composition, said comb polymer having pendant groups comprising ethylene oxide (EO), propylene oxide groups (PO), or mixture thereof; said comb polymer capable of being absorbed by smectite clay which expands when in contact with water and thereupon absorbs said comb polymer; and  
       (B) an agent operative to modify clay activity to minimize said absorption of said comb polymer, said agent being selected from the group consisting of  
       an inorganic cation selected from the group consisting of magnesium, aluminum, iron, K + , NH 4   + , Cs + , Rb + , and Fr + ;  
       an organic cation selected from the group consisting of (i) an organic group bonded to a cationic salt group selected from phosphonium, pyridinium, sulfonium and quaternary ammonium; and (ii) an organic compound containing a single cationic amine salt group;  
       a polar organic molecule selected from the group consisting of an oxyalkylene having a different molecular structure from said plasticizer of component A, a crown ether, a polyvinyl alcohol, a polyacrylic acid having a molecular weight of 2,000 or less, a polymethacrylic acid having a molecular weight of 2,000 or less, a polyacrylate having a molecular weight of 2,000 or less, and a polymethacrylate having a molecular weight of 2,000 or less; and  
       a clay dispersant operative to reduce absorptivity of said clay, said dispersant comprising a polyphosphate.  
     
     
       2. The admixture composition of  claim 1  wherein said comb polymer comprises ethylene oxide and propylene oxide groups. 
     
     
       3. The admixture composition of  claim 1  wherein said agent is an inorganic cation. 
     
     
       4. The admixture composition of  claim 1  wherein said agent is a multi-valent inorganic cation. 
     
     
       5. The admixture composition of  claim 1  wherein said agent is an oxyalkylene molecule having a molecular structure different from said comb polymer. 
     
     
       6. The admixture composition of  claim 1  wherein said agent is a monovalent inorganic cation. 
     
     
       7. The admixture composition of  claim 1  wherein said agent is an organic cation. 
     
     
       8. The admixture composition of  claim 7  wherein said agent is an organic cation. 
     
     
       9. The admixture composition of  claim 1  wherein said amine further comprises an oxyalkylene group. 
     
     
       10. The admixture composition of  claim 1  wherein said agent is a polar organic molecule capable of being absorbed by a clay. 
     
     
       11. The admixture composition of  claim 10  further comprising a gluconate, a heptagluconate, a heptaglyconic acid, a gluconic acid, a corn syrup, or a mixture thereof. 
     
     
       12. The admixture composition of  claim 11  wherein said polar organic molecule agent is an oxyalkylene. 
     
     
       13. The admixture composition of  claim 12  wherein said clay activity modifying agent is a a comb polymer having pendant ethylene oxide and propylene oxide groups with an average molecular weight less than 1000. 
     
     
       14. The admixture composition of  claim 1  wherein said agent is a clay dispersant. 
     
     
       15. The admixture composition of  claim 1  wherein said agent is a polyphosphate selected from the group of metaphosphate, tripolyphosphate, and pyrophosphate. 
     
     
       16. An admixture composition comprising: 
       (A) a comb polymer operative to plasticized a hydratable cementitious compostion, said comb polyrmer having pendant comprising ethylene oxide (EO), propylene oxide groups (PO), or mixture thereof, said comb polymer capable of being absorbed by smectite clay which expands when in contact with water and there upon absorbs said comb polymer; and  
       (B) an agent operative to modify clay activity, said agent comprising a polar orgainic molecule, said polar organic molecule comprising an oxyalkylene having a different molecular structure from said comb polymer of component A.  
     
     
       17. The admixture composition of  claim 16  further comprising a gluconic acid or gluconate.